pyglet.clock
Precise framerate calculation function scheduling.
The clock
module allows you to schedule functions
to run periodically, or for one-shot future execution. pyglet’s default
event loop (run()
) keeps an internal instance of
a Clock
, which is ticked automatically.
Note
Some internal modules will schedule items on the clock. If you are using a custom event loop, always remember to tick the clock!
Scheduling
You can schedule a function to be called every time the clock is ticked:
def callback(dt):
print(f"{dt} seconds since last callback")
clock.schedule(callback)
The schedule_interval method causes a function to be called every “n” seconds:
clock.schedule_interval(callback, 0.5) # called twice a second
The schedule_once method causes a function to be called once “n” seconds in the future:
clock.schedule_once(callback, 5) # called in 5 seconds
All the schedule methods will pass on any additional args or keyword args you specify to the callback function:
def move(dt, velocity, sprite):
sprite.position += dt * velocity
clock.schedule(move, velocity=5.0, sprite=alien)
You can cancel a function scheduled with any of these methods using unschedule:
clock.unschedule(move)
Using multiple clocks
The clock functions are all relayed to an instance of
Clock
which is initialised with the module. You can
get this instance to use directly:
clk = pyglet.clock.get_default()
You can also replace the default clock with your own:
myclk = pyglet.clock.Clock() pyglet.clock.set_default(myclk)
Each clock maintains its own set of scheduled functions and frequency measurement. Each clock must be “ticked” separately.
Multiple and derived clocks potentially allow you to separate “game-time” and “wall-time”, or to synchronise your clock to an audio or video stream instead of the system clock.
- class Clock
- __init__(
- time_function: ~typing.Callable = <built-in function perf_counter>,
Initialise a Clock, with optional custom time function.
You can provide a custom time function to return the elapsed time of the application, in seconds. Defaults to
time.perf_counter
, but can be replaced to allow for easy time dilation effects or game pausing.
- call_scheduled_functions(dt: float) bool
Call scheduled functions that elapsed on the last update_time.
This method is called automatically when the clock is ticked (see
tick()
), so you need not call it yourself in most cases.- Parameters:
dt (
float
) – The elapsed time since the last update to pass to each scheduled function. This is not used to calculate which functions have elapsed.- Return type:
Returns:
True
if any functions were called, elseFalse
.
- get_frequency() float
Get the average clock update frequency of recent history.
The result is the average of a sliding window of the last “n” updates, where “n” is some number designed to cover approximately 1 second. This is the clock frequence, not the Window redraw rate (fps).
- Return type:
- get_sleep_time(sleep_idle: bool) float | None
Get the time until the next item is scheduled, if any.
Applications can choose to continue receiving updates at the maximum framerate during idle time (when no functions are scheduled), or they can sleep through their idle time and allow the CPU to switch to other processes or run in low-power mode.
If
sleep_idle
isTrue
the latter behaviour is selected, andNone
will be returned if there are no scheduled items.Otherwise, if
sleep_idle
isFalse
, or if any scheduled items exist, a value of 0 is returned.
- schedule( ) None
Schedule a function to be called every tick.
The scheduled function should have a prototype that includes
dt
as the first argument, which gives the elapsed time in seconds since the last clock tick. Any additional args or kwargs given to this method are passed on to the callback:def callback(dt, *args, **kwargs): pass
- Return type:
Note
Functions scheduled using this method will be called every tick by the default pyglet event loop, which can lead to high CPU usage. It is usually better to use
schedule_interval()
unless this is desired.
- schedule_interval( ) None
Schedule a function to be called every
interval
seconds.To schedule a function to be called at 60Hz (60fps), you would use
1/60
for the interval, and so on. If pyglet is unable to call the function on time, the schedule will be skipped (not accumulated). This can occur if the main thread is overloaded, or other hard blocking calls taking place.The callback function prototype is the same as for
schedule()
. :rtype:None
Note
Specifying an interval of
0
will prevent the function from being called again. If you want to schedule a function to be called as often as possible, seeschedule()
.
- schedule_interval_for_duration( ) None
Temporarily schedule a function to be called every
interval
seconds.This method will schedule a function to be called every
interval
seconds (seeschedule_interval()
), but will automatically unschedule it afterduration
seconds.The callback function prototype is the same as for
schedule()
.- Args:
- func:
The function to call when the timer lapses.
- interval:
The number of seconds to wait between each call.
- duration:
The number of seconds for which the function is scheduled.
- Return type:
- schedule_interval_soft( ) None
Schedule a function to be called approximately every
interval
seconds.This method is similar to
schedule_interval()
, except that the clock will move the interval out of phase with other scheduled functions in order to distribute CPU load more evenly.This is useful for functions that need to be called regularly, but not relative to the initial start time.
pyglet.media
does this for scheduling audio buffer updates, which need to occur regularly – if all audio updates are scheduled at the same time (for example, mixing several tracks of a music score, or playing multiple videos back simultaneously), the resulting load on the CPU is excessive for those intervals but idle outside. Using the soft interval scheduling, the load is more evenly distributed.Soft interval scheduling can also be used as an easy way to schedule graphics animations out of phase; for example, multiple flags waving in the wind.
- Return type:
- schedule_once( ) None
Schedule a function to be called once after
delay
seconds.The callback function prototype is the same as for
schedule()
.- Return type:
- tick(poll: bool = False) float
Signify that one frame has passed.
This will call any scheduled functions that have elapsed, and returns the number of seconds since the last time this method has been called. The first time this method is called, 0 is returned.
- get_default() Clock
Get the pyglet default Clock.
Return the
Clock
instance that is used by all module-level clock functions.- Return type:
- set_default(default: Clock) None
Set the default clock to use for all module-level functions.
By default, an instance of
Clock
is used.- Return type: